1. Field of the Invention
The present invention relates to a distance measuring equipment for measuring a distance up to a target to be measured in distance using a semiconductor photo detector element such as a silicon photo diode (SPD), and a camera incorporated thereinto such a distance measuring equipment.
2. Description of the Related Art
Hitherto, there is widely spread a camera incorporating thereinto an automatic focusing (AF) device, which is generally referred to as an active type. Such an active type of automatic focusing device adopts a system for measuring a distance up to a camera subject in such a manner that an AF light projection unit and an AF photo detection unit are disposed at intervals of a predetermined base length, light is projected from the AF light projection unit to the camera subject, and light reflected on the camera subject is detected by the AF photo detection unit. As a photo detector element for focusing, for example, a semiconductor element such as an SPD element, which will be described later, is used. In some case, a camera is provided with an automatic flash emission device (an automatic electronic flash device) in which at the time of a photography a flash is projected to a camera subject, a reflected light from the camera subject is detected, and a flash emission is stopped at a timing that the reflected light reaches a predetermined light quantity, and a remote control device for instructing an execution of an operation (for example, a self-timer operation) according to a received light from a remote control equipment (for example, for a self-timer) for controlling the camera in accordance with an emission of light directed to the camera, as well as an automatic focusing device. In such a case, in the camera, the automatic electronic flash device and the remote control device are provided with semiconductor photo detector elements represented by the SPD element, in addition to the semiconductor photo detector element for the automatic focus (AF).
FIG. 9 is a diagram of semiconductor photo detector elements incorporated into the respective devices and their associated circuits, with respect to the conventional camera.
In FIG. 9, there are shown an SPD 60, which is one example of the semiconductor photo detector element for the automatic focus (AF), and an AF-dedicated photo detector circuit 62, which are provided in an automatic focusing device; and an SPD 63 provided in another device and a dedicated photo detector 64 for the another device. The AF-dedicated photo detector 62 and the dedicated photo detector circuit 64 are connected to an MPU (Micro Processor Unit) 65 serving as a control unit. Here, there will be explained a case where the camera is provided with an automatic electronic flash device as the xe2x80x9canother devicexe2x80x9d.
The SPD 60 shown in FIG. 9 has a detection surface 61 which is divided into two detection areas. The SPD 60 generates a photo-current in such a manner that light for focusing is projected from an AF light projection unit (not illustrated) to a camera subject and the light for focusing reflected on the camera subject is detected on the two detection areas of the detection surface 61. The photo-current thus generated is separated into photo-currents I1 and I2 in accordance with light quantities irradiated onto the two detection areas of the detection surface 61, respectively, and the photo-currents I1 and I2 are fed to the AF-dedicated photo detector circuit 62. The AF-dedicated photo detector circuit 62 determines a distance up to the camera subject in accordance with both the photo-currents I1 and I2. The MPU 65 controls a lens driving for focusing in accordance with the distance thus determined.
On the other hand, the SPD 63 detects the reflected light from the camera subject through the flash projected to the camera subject from an automatic electronic flash device at the time of photography. A photo-current I3 generated through the detection by the SPD 63 conducts via the dedicated photo detector circuit 64. The dedicated photo detector circuit 64 integrates the photo-current I3 and outputs a signal to stop the flashing operation of the automatic electronic flash device in the timing that the integrated photo-current I3 reaches a predetermined quantity of reflected light. This signal is transmitted to the MPU 65 as well as a flash emission stop control unit (not illustrated). The MPU 65 performs a control of shutter closing and the like in accordance with this signal.
As mentioned above, in some case, the conventional camera is provided with an automatic electronic flash device and a remote control device as well as an automatic focusing device. In such a camera, although the photo detection wavelengths of those devices are mutually closed, those devices are individually provided with their dedicated photo detector elements. Thus, the conventional camera is associated with a problem that the number of photo detector elements is increased, and as a result a circuit scale is enlarged. Accordingly, there is also raised a problem that the cost is increased.
Further, there is proposed a technology (cf. Japanese Patent Application Laid Open Gazette Hei.7-260475) in which in stead of the AF-dedicated photo detector circuit 62, the signal of the photo-current is subjected to an A/D conversion and then is operated. However, also in accordance with this technology, the number of photo detector elements is not decreased. This technology is also associated with a problem that the cost is increased.
In order to solve those problems, it is considered that one semiconductor photo detector element is used on a common basis for the automatic focusing device and another device. However, control and processing method for photo detection signals in the automatic focusing device are different from those in another device, for example, an automatic electronic flash device. Therefore, it is difficult for another device to use an AF-dedicated photo detector circuit for processing photo-current from the semiconductor photo detector element as a photo detector circuit as it is.
Further, the camera incorporated therein an automatic focusing device is also associated with an additional problem that as to focusing for distance, an accuracy of focusing is lowered.
In view of the foregoing, it is an object of the present invention to provide a distance measuring equipment capable of enhancing an accuracy of focusing, and a camera capable of enhancing an accuracy of focusing and/or reducing a cost with a small scale of circuit.
To achieve the above-mentioned object, the present invention provides a distance measuring equipment comprising:
a light projecting unit for projecting light for a distance measurement; and
a photo detector unit, having a light detection window disposed at an interval of a predetermined distance from said light projecting unit in a direction intersecting with a direction of travel of light projected from said light projecting unit, for determining a distance up to a subject in such a manner that light is projected from said light projecting unit, and light reflected on the subject is detected through said light detection window,
wherein said photo detector unit comprises:
a semiconductor photo detector element comprising a detection surface for generating a photo-current upon receipt of irradiation of light, signal electrodes, connected to associated divided areas of said detection surface, respectively, adapted for outputting the photo-current generated by irradiation of light onto said detection surface, and a first switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal;
a first distance arithmetic unit for determining a distance up to the subject in accordance with a plurality of photo-currents derived through said signal electrodes, in a state that said first switch is changed over to the second state; and
a second distance arithmetic unit for determining a distance up to the subject in accordance with the photo-current derived through a first signal electrode which is one of said signal electrodes, in a state that said first switch is changed over to the first state.
According to the distance measuring equipment of the present invention as mentioned above, there are provided the first and second distance arithmetic units for determining a distance up to the subject in accordance with the mutually different focusing algorithms. Thus, it is possible to extend a possible focusing range of distance and also possible to perform a distance measurement with greater accuracy.
In the semiconductor photo detector element, which is used in the distance measuring equipment of the present invention as mentioned above, it is acceptable that said semiconductor photo detector element further comprises a second switch, provided in association with another signal electrode excepting said first signal electrode, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct into the associated signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting into the associated signal electrode, in accordance with a control signal,
said first distance arithmetic unit determines a distance up to the subject in accordance with a plurality of photo-currents derived through said signal electrodes, in a state that said first switch is changed over to the second state, and said second switch is changed over to the first state, and
a second distance arithmetic unit for determining a distance up to the subject in accordance with the photo-current derived through said first signal electrode, in a state that said first switch is changed over to the first state, and said second switch is changed over to the second state.
In the distance measuring equipment of the present invention as mentioned above, it is acceptable that said semiconductor photo detector element further comprises a switch element, provided in association with another signal electrode excepting said first signal electrode of said signal electrodes, and connected to the associated signal electrode, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated signal electrode, in accordance with a control signal,
said first distance arithmetic unit determines a distance up to the subject in accordance with a plurality of photo-currents derived through said signal electrodes, in a state that said first switch is changed over to the second state, and said switch element is changed over to the first state, and
a second distance arithmetic unit for determining a distance up to the subject in accordance with the photo-current derived through said first signal electrode, in a state that said first switch is changed over to the first state, and said switch element is changed over to the second state.
In the distance measuring equipment of the present invention as mentioned above, and a camera of the present invention, which will be described later, said first state is a low impedance state, and said second state is a high impedance state. However, the first state and the second state are not always restricted to the low impedance state and the high impedance state, but the first state is a state that permits the photo-current generated on the detection surface to conduct through a switch, and the second state is a state that inhibits the photo-current generated on the detection surface from conducting through the switch.
To achieve the above-mentioned object, the present invention provides a first camera loaded with a distance measuring equipment comprising a light projecting unit, having a light projection window disposed in front of the camera, for projecting light for focusing from said light projection window in front of the camera, and a photo detector unit, having a light detection window disposed in front of the camera and at an interval of a predetermined distance from said light projection window, for determining a distance up to a subject in such a manner that light is projected from said light projection window in front of the camera, and light reflected on the subject is detected through said light detection window,
wherein said photo detector unit comprises:
a semiconductor photo detector element comprising a detection surface for generating a photo-current upon receipt of irradiation of light, signal electrodes, connected to associated divided areas of said detection surface, respectively, adapted for outputting the photo-current generated by irradiation of light onto said detection surface, and a first switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal;
a control unit for generating a control signal to change over said first switch and transmitting the control signal to said semiconductor photo detector element;
a first distance arithmetic unit for determining a distance up to the subject in accordance with a plurality of photo-currents derived through said signal electrodes, in a state that a control signal to change over said first switch to said second state is transmitted to said semiconductor photo detector element by said control unit; and
a second distance arithmetic unit for determining a distance up to the subject in accordance with the photo-current derived through a first signal electrode which is one of said signal electrodes, in a state that a control signal to change over said first switch to said first state is transmitted to said semiconductor photo detector element by said control unit.
According to the first camera of the present invention as mentioned above, there are provided the first and second distance arithmetic units for determining a distance up to the subject in accordance with the mutually different focusing algorithms. Thus, it is possible to extend a possible focusing range of distance and also possible to perform a distance measurement with greater accuracy.
For example, according to an embodiment of the present invention which will be described later, in the event that a photography is performed at the relatively short distance, the first switch of the semiconductor photo detector element is switched by the control unit to offer the high impedance state which is an example of the first state mentioned above. Thus, the first distance arithmetic unit determines a distance up to a subject in accordance with both the photo-currents obtained through the pair of signal electrodes of the semiconductor photo detector element. On the other hand, in the event that a photography is performed at the relatively long distance, the first switch of the semiconductor photo detector element is switched by the control unit to offer the low impedance state which is an example of the second state mentioned above. Thus the second distance arithmetic unit determines a distance up to a subject in accordance with photo-current obtained from one of the pair of signal electrodes of the semiconductor photo detector element. In this manner, in the event that a photography is performed at the relatively long distance, there is performed a processing of determining a distance up to the subject in accordance with a total quantity of light. Thus, it is possible to enhance accuracy of focusing in focusing of the long distance.
To achieve the above-mentioned object, the present invention provides a second camera loaded with a flash emission device in which at time of a photography a flash is projected to a subject, a reflected light from the subject is detected, and a flash emission is stopped at a timing that the reflected light reaches a predetermined light quantity, and a distance measuring equipment comprising a light projecting unit, having a light projection window disposed in front of the camera, for projecting light for focusing from said light projection window in front of the camera, and a photo detector unit, having a light detection window disposed in front of the camera and at an interval of a predetermined distance from said light projection window, for determining a distance up to a subject in such a manner that light is projected from said light projection window in front of the camera, and light reflected on the subject is detected through said light detection window,
wherein said camera comprises:
a semiconductor photo detector element comprising a detection surface for generating a photo-current upon receipt of irradiation of light, signal electrodes, connected to associated divided areas of said detection surface, respectively, adapted for outputting the photo-current generated by irradiation of light onto said detection surface, and a first switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal, said semiconductor photo detector element being used on a common basis for said flash emission device and said distance measuring equipment and serving to detect both flash reflected on the subject and incident through said light detection window and light for focusing reflected on the subject and incident through said light detection window; and
a control unit for generating a control signal to change over said first switch between said first state and said second state and transmitting the control signal to said semiconductor photo detector element.
According to the second camera of the present invention as mentioned above, there is adopted the semiconductor photo detector element having the above-mentioned first switch. That is, the semiconductor photo detector element is used on a common basis for the flash emission device and the distance measuring equipment. This feature makes it possible for the semiconductor photo detector element to serve to detect both flash reflected on the subject and light for focusing reflected on the subject. Thus, according to the second camera of the present invention, as compared with the conventional camera in which photo detector elements are provided individually for the flash emission device and the distance measuring equipment, it is possible to reduce the number of photo detector elements.
To achieve the above-mentioned object, the present invention provides a third camera loaded with a remote control device responsive to light from a remote control equipment for controlling the camera in accordance with an emission of light directed to the camera for instructing an execution of operation according to detection of the light, and a distance measuring equipment comprising a light projecting unit, having a light projection window disposed in front of the camera, for projecting light for focusing from said light projection window in front of the camera, and a photo detector unit, having a light detection window disposed in front of the camera and at an interval of a predetermined distance from said light projection window, for determining a distance up to a subject in such a manner that light is projected from said light projection window in front of the camera, and light reflected on the subject is detected through said light detection window,
wherein said camera comprises:
a semiconductor photo detector element comprising a detection surface for generating a photo-current upon receipt of irradiation of light, signal electrodes, connected to associated divided areas of said detection surface, respectively, adapted for outputting the photo-current generated by irradiation of light onto said detection surface, and a first switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal, said semiconductor photo detector element being used on a common basis for said remote control device and said distance measuring equipment and serving to detect both light emitted from said remote control equipment and incident through said light detection window and light for focusing reflected on the subject and incident through said light detection window; and
a control unit for generating a control signal to change over said first switch between said first state and said second state and transmitting the control signal to said semiconductor photo detector element.
According to the third camera of the present invention as mentioned above, there is adopted the semiconductor photo detector element having the above-mentioned first switch. This feature makes it possible for the semiconductor photo detector element to serve to detect both light emitted from the remote control equipment and light for focusing reflected on the subject. Thus, according to the third camera of the present invention, as compared with the conventional camera in which photo detector elements are provided individually for the remote control device and the distance measuring equipment, it is possible to reduce the number of photo detector elements.
To achieve the above-mentioned object, the present invention provides a fourth camera loaded with a remote control device responsive to light from a remote control equipment for controlling the camera in accordance with an emission of light directed to the camera for instructing an execution of operation according to detection of the light, a flash emission device in which at time of a photography a flash is projected to a subject, a reflected light from the subject is detected, and a flash emission is stopped at a timing that the reflected light reaches a predetermined light quantity, and a distance measuring equipment comprising a light projecting unit, having a light projection window disposed in front of the camera, for projecting light for focusing from said light projection window in front of the camera, and a photo detector unit, having a light detection window disposed in front of the camera and at an interval of a predetermined distance from said light projection window, for determining a distance up to a subject in such a manner that light is projected from said light projection window in front of the camera, and light reflected on the subject is detected through said light detection window,
wherein said camera comprises:
a semiconductor photo detector element comprising a detection surface for generating a photo-current upon receipt of irradiation of light, signal electrodes, connected to associated divided areas of said detection surface, respectively, adapted for outputting the photo-current generated by irradiation of light onto said detection surface, and a first switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal, said semiconductor photo detector element being used on a common basis for said remote control device, said flash emission device and said distance measuring equipment and serving to detect three types of light emitted from said remote control equipment and incident through said light detection window, flash reflected on the subject and incident through said light detection window and light for focusing reflected on the subject and incident through said light detection window; and
a control unit for generating a control signal to change over said first switch between said first state and said second state and transmitting the control signal to said semiconductor photo detector element.
According to the fourth camera of the present invention as mentioned above, there is adopted the semiconductor photo detector element having the above-mentioned first switch. This feature makes it possible for the semiconductor photo detector element to serve to detect three types of light emitted from the remote control equipment, flash reflected on the subject and light for focusing reflected on the subject. Thus, according to the fourth camera of the present invention, as compared with the conventional camera in which photo detector elements are provided individually for the remote control device, the flash emission device and the distance measuring equipment, it is possible to reduce the number of photo detector elements.
In any of the first to fourth cameras of the present invention as mentioned above, it is acceptable that said semiconductor photo detector element further comprises a second switch, provided in association with another signal electrode excepting the first signal electrode which is one of said signal electrodes, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct into the associated signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated signal electrode, in accordance with a control signal, and
said control unit generates a control signal to change over said first switch and said second switch in such a manner that when one of said first switch and said second switch is in the first state, another switch is in the second state, and transmits the control signal to said semiconductor photo detector element.
In any of the first to fourth cameras of the present invention as mentioned above, it is acceptable that said semiconductor photo detector element further comprises a switch element, provided in association with another signal electrode excepting the first signal electrode of said signal electrodes, and connected to the associated signal electrode, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated signal electrode, in accordance with a control signal, and
said control unit generates a control signal to change over said first switch and said switch element in such a manner that when one of said first switch and said switch element is in the first state, another switch is in the second state, and transmits the control signal to said semiconductor photo detector element and said switch element.